1. Field of the Invention
The invention relates to an electrical plug-in connector in accordance with the preamble of claim 1.
2. Description of the Related Art
Plug-in connectors generally serve for electrical connection between electrical components or electrical circuits. In electronics, circuit boards as circuit carriers have attained outstanding significance. With the aid of electrical plug-in connectors a reliable, generally releasable electrical connection between circuit carriers mostly being planar circuit boards may be established. The circuit board-side terminals of plug-in connectors are designed such that through suitable processing methods a secure electrical and mechanical connection may be produced between these plug-in connector terminals and, the circuit board. Processes to be mentioned here are the classical flow-soldering technique, the surface soldering technique (≈SMT=surface mount technology) and the press-fitting technique. In the cases of flow-soldering method and press-fitting technique the plug-in connector terminal is introduced into a feedthrough. This is referred to as through-hole technology. A feedthrough is part of the circuit located on the circuit board and consists of a bore in the circuit board material that is covered with conductive material and customarily arranged at right angles with the circuit board surface.
The flow soldering method takes the circuit board having—besides other electronic components—one or several plug-in connectors pre-mounted on it over a stationary wave of flowing, liquid solder. The solder consists of a tin alloy heated above melting point. As the bottom side of the circuit board with the soldering tags of the plug-in connectors slightly protruding from the feedthroughs thereof contacts the liquid solder, the solder is drawn into the feedthrough by capillary action and subsequently by cooling becomes a connection having mechanical strength and good electrical conductivity.
The surface soldering technique is a related process which does, however, customarily not utilize feedthroughs. Circuit boards in surface technique include conductor paths of copper forming part of the circuit board's circuitry. The ends of such paths are geometrically designed for the surface soldering technique such that a corresponding electronic or electro-mechanical component adapted for the surface soldering technique may match these path ends with its connecting pads. Prior to mounting of the surface mounting components, the ends of the conduction paths are coated with a highly viscous, sticky solder paste by means of a screen printing method, which solder paste is capable of sufficient mechanical immobilization of the subsequently applied component until the surface soldering process is performed. The solder paste is composed of very small solder globules consisting of a tin alloy with a sticky additive that ensures adhesion of the surface mounting element on the circuit board until the soldering process, and further additives intended to improve operability. As a result of the heat supplied to the soldering location during the surface soldering process, the scolder paste melts and in the subsequent cooling process forms a mechanically stable soldered joint with good electrical conductivity between component terminal and conduction path. The adhesive and the additives added to the solder paste evaporate in the process. Heat transport to the soldering location in the surface soldering process is alternatively effected through various techniques, such as by infrared radiation or by convection. The convection soldering process has attained the highest significance in this field.
For components having larger dimensions or a higher weight, such as for instance plug-in connectors, the combination of surface soldering technique and flow soldering method is employed. Here the feedthroughs already known from the flow soldering method are introduced into the circuit board for these components in addition to the surface soldering terminations. These feedthroughs are coated by the printing process customary for the surface soldering technique. If proceeding in a suitable manner, the solder paste is applied not only onto the feedthrough but also pressed into it. Following pre-mounting of the component, both the component soldering terminations and the solder paste are then located in the feedthrough.
Patent specification EP 0 422 785 B1 shows a plug-in connector constructed of a plurality of wafers sequentially carrying the electrical contacts, and a carrier insulating body. The terminals are realized in press-fitting technique. Document EP 0 638 967 A2 shows a similar design where the circuit board terminals are executed in press-fitting technique. U.S. Pat. No. 3,539,974 shows a plug-in connector assembly constructed of wafers manufactured of insulating material and conductive elements integrated into these wafers. The terminals of this plug-in connection are suited for the flow soldering method.
The advantage of realizing the above mentioned plug-in connector designs is the high mechanical stability of the plug-in connector and the positional accuracy of the soldering tags which is ensured by the fact that the soldering tag is routed through its sheath through insulating material as far as to the soldering location.
The just-mentioned plug-in connectors do, however, exhibit essential drawbacks for the surface soldering process. The named solutions do not, or only insufficiently, allow the supply of a sufficient amount of heat to the soldering location in the short time available for the surface soldering process.